The research involves a spectroscopic study of model visual pigments. This will include (1) absorption spectra and theoretical calculations relating to the effect of protonation of the nitrogen and the existence of negative point charges near the carbons of retinal Schiff bases, (2) evaluation of quantum yield and lifetimes of some retinols and the use of these relative to dynamics of excited states, (3) an attempt to determine the basis of the sensitivity of the quantum yields of fluorescence and intersystem crossing to the magnitude of solvent H-bonding ability, (4) determination of the quantum yields and lifetimes of some cis protonated Schiff bases (alkylamine) and if possible for amino acid Schiff bases. These results will be used to interpret the spectroscopic properties of rhodopsin and (5) attempt to decide the nature of and/or the difference in the state couplings of retinals and retinols as related to the significant difference in quantum yields. BIBLIOGRAPHIC REFERENCES: Carbon-13 Magnetic Resonance Investigation of Retinal Isomers and Related Compounds, R.S. Becker, S. Berger, W.K. Walling, W.M. Grant and R.J. Pugmire, J. Am. Chem. Soc., 96, 7008 (1974). 2. Visual Pigments V. Ground and Excited State Acid Dissociation Constants of Protonated All-Trans Retinal Schiff Base and Correlation with Theory, A.M. Schaffer, T. Yamaoka and R.S. Becker, Photochem. Photobiol., 21, 297 (1975).